CLL exosomes increase CLL cell adhesion and survival in vitro and promote tumor growth in vivo. (A) Primary CLL cells labeled with PKH67 dye were added for 3 hours to cultures of HS-5 or HMEC-1 cells untreated (Ctrl) or pretreated 24 hours with 50 µg/mL of CLL exosomes (MEC-1; Exo). After 5 washes, images were taken via fluorescence microscopy. (Left) Representative images are shown. Scale bar, 100 µm. (Right) Quantification of CLL cell adhesion (n = 3). *P < .05, **P < .01. (B) CLL cells incubated with supernatants of BM-MSCs untreated (SN Ctrl) or treated for 24 hours with 50 µg/mL CLL exosomes (SN Exo). Cell viability was assessed after 6 days using CCK8 assay. Data are reported as the percentage relative to SN Ctrl (n = 3). **P < .01. (C) Primary CLL cells were treated with indicated cytokines (10 ng/mL) and viability was assessed after 6 days using CCK8 assay. Data are reported as the percentage relative to Ctrl (n = 9). *P < .05, **P < .01, ***P < .001. (D and E) PBS (Ctrl) or 100 µg CLL exosomes (Exo) were mixed with 5 × 10⁶ MEC-1-eGFP cells and subcutaneously injected into eight NSG mice. (D) (Left) Representative images of subcutaneous tumors removed from NSG mice. Scale bar, 5 mm. (Right) Quantification of tumor volume in mm³. *P < .05. (E) (Left) Representative images of kidneys (NSG mice). Scale bar, 5 mm. (Center) Representative flow cytometry plots showing MEC-1-eGFP cells (black gate) in kidneys. (Right) Quantification of GFP positive cells in kidneys.*P < .05.